This application is a national stage entry under 35 U.S.C. § 371 of PCT/JP04104435, filed Mar. 29, 2004, (designating the U.S.; and which published in Japanese in WO 2004/088404 on Oct. 14, 2004), which claims the benefit of Japanese Patent Application Nos. 2003-094036, filed Mar. 31, 2003 and 2003-178980, filed Jun. 24, 2003, the entire contents of both applications are expressly incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display device, more particularly to a liquid crystal display device including a housing that covers the backside of a display section and a circuit board provided on the backside of the housing.
2. Prior Art
Liquid crystal display devices are widely used as display devices for cell phones, personal computers, car navigation systems, television sets, and various kinds of office automation equipment because they are lighter, consume less power and require less space compared to other display devices.
On the other hand, due to continuing innovations, multi-functional and high-powered equipment which are also economical and convenient to use have proliferated, but this has also led to a continuing demand for display devices that are lighter and occupy minimum space, have better quality and consume less power. For example, since the installation space for a liquid crystal display device used in car navigation systems of 1DIN (50 mm(height)×178 mm(width)) is limited, the need to come up with a slim and small display device which is at the same time easy to attach and impervious to dust has become imperative.
Further, an illumination unit provided with various kinds of light source is usually attached to liquid crystal display devices to realize a bright display screen, and the illumination unit irradiates the back of the display panel of the liquid crystal display device. The illumination unit is roughly classified in two different types depending on the attaching position of the light source. One is an edge light type where the linear light source is arranged along the surface of one side edge of a light-guiding plate, and the other is a direct type where the light source is arranged on the backside of the light-guiding plate. Between the two, the edge light type is largely adopted for equipment which give priority to slim profiles because of their superior features of slimness and uniformity of surface luminance. On the other hand, the direct type which provides a large-sized light source, is adopted for equipment requiring high levels of brightness.
Although these types of liquid crystal display devices have further become smaller, slimmer and lighter in recent years, devices equipped with a backlight have also become essential. It has become possible to make such devices smaller and slimmer by constructing individual parts constituting the backlight, such as the light source, light-guiding plate, a housing and the like, smaller, slimmer and lighter, and by arranging their wiring within the housing.
For example, Japanese Laid-Open Patent Publication No. 2001-249621 introduces an illumination unit that is designed to house lead wires connected to a light source efficiently in a housing.
The illumination unit UT, as shown in FIG. 8, includes a light source 102, a light-guiding plate 101 that guides the light coming from the light source 102, and a metal housing 104 arranged below and on the two short sides of the light-guiding plate 101 upon which the unit is constituted, and lead wires 103 connected to the light source 102 being sandwiched between the surface of one side of the light-guiding plate 101 and the housing 104, and the lead wires 103 are held by a plurality of protrusions K to prevent them from becoming disengaged from the housing.
However, since this illumination unit is designed in such manner that a gap is provided between the surface of one side of the light-guiding plate and the housing and the lead wires are housed in the gap, it is necessary to make the housing larger to provide for such housing space, and accordingly, the display device becomes larger.
Further, a small-sized backlight without using sheet wiring as electric wire to be connected to the light source is also disclosed in Japanese Laid-Open Patent Publication No. 2002-150823.
Such backlight, represented as backlight 110 in FIG. 9, includes a light-guiding plate 111 where the surface of the edge of one side thereof (hereinafter, the “Side Edge Surface”) is an incident surface, a linear light source 112 provided in horizontal directions along the side edge surface being the incident surface, and a lead wire 113 is connected to one side in the longitudinal direction of the linear light source 112, and is extended to the other end in the longitudinal direction of the linear light source 112. Then, the light-guiding plate 111 has an inclined backside and is arranged in such manner such that its thickness diminishes as it is drawn away from the incident surface and the space below the backside of the light-guiding plate becomes larger as the thickness of the plate diminishes. Further, the lead wire 113 passes through the backside of the light-guiding plate 110 under the condition that a gap T from the incident surface is maintained and extends to the end of the other side of the linear light source 112 in the longitudinal direction, and is positioned in the space below the light-guiding plate, which space becomes larger as the light-guiding plate becomes thinner, and a part of the lead wire 113 is disposed above the lower portion of the side edge surface of the light-guiding plate, which is the incident surface.
The resulting display device with this kind of wiring structure is still quite thick because the lead wire is arranged below a lower frame at the gap T from the incident surface. However, if such thickness is reduced, the size of the lead wire is effectively restricted.
Further, this type of liquid crystal display device is provided with a connector for receiving signals for images or the like. The connector is provided on the backside of the liquid crystal panel in most cases, but such positioning gives rise to various problems.
For example, Japanese Laid-Open Patent Publication No. 2002-351349 discloses a liquid crystal display device where the connection state of the connector can be easily verified. Specifically, a liquid crystal cell and a backlight are enclosed by a frame, the top surface of the liquid crystal cell being covered with a front bezel cover (outer frame), while the bottom surface thereof is covered with a rear bezel cover, and a check hole corresponding to the connector of a control circuit board is formed somewhere on the rear bezel cover. As a result, the connection state of the connector can be easily determined through the check hole.
However, when the liquid crystal display device described in Japanese Laid-Open Patent Publication No. 2002-351349 is used for applications where slimness is required as in vehicular navigation systems, for example, since connection to the connector of the liquid crystal display device is provided on the backside of the liquid crystal display device and is done in such a manner that wiring is installed away from the dashboard of a vehicle, operability is very poor because the connector is invisible. Accordingly, breakage of the connector or defective connection occurs frequently.